Geology topics

H. Wedow

Publications and source records attributed to H. Wedow.

4 recordsLinked to original sources

USGS1971

An early middle ordovician age for collapse breccias in the east Tennessee zinc districts as indicated by compaction and porosity features

The carbonate strata of the Lower Ordovician formations in the southern Appalachian Valley were probably considerably thicker, less compacted, and more porous and permeable in early Middle Ordovician time than they are now. Analysis of selected compaction features of rocks associated with the breccias of the East Tennessee zinc districts permits quantitative estimation of the relative compaction (reduction in thickness) these sediments have undergone before and after brecciation. Total reduction in thickness of certain Lower Ordovician marker beds because of compaction during burial under younger Paleozoic sedimentary rocks and imbricate Appalachian thrust sheets appears to be at least some 40 to 50 percent. Furthermore, it is also estimated that about half of this compaction took place after brecciation in the solution-collapse structures of the zinc deposits. In comparison with laboratory compaction tests on carbonate muds it is apparent that the Lower Ordovician rocks had been buried to a depth of at least several thousand feet by the end of the Paleozoic Era. On the other hand the zones of collapse breccias probably formed at depths of generally less than a thousand feet, thus indicating an early Middle Ordovician age for their development. The general character of the rock during this time probably was similar to that of Tertiary limestone, which acts as the principal aquifer in the Coastal Plain region of southeastern United States.

Tennessee↗

USGS1971

Models of mineralized solution-collapse structures from drilling statistics: An aid to exploration

Variations in thickness and metal content of selected stratigraphic units cut by drill holes in the East Tennessee zinc districts have been analyzed by regression techniques. Such analysis demonstrated that as the thickness of an underlying limestone unit is decreased chiefly by solution thinning, overlying fine-grained dolomite units increase in thickness by collapse dilation. Variation in metal content is closely associated with this inverse thickness relationship because of the deposition of the ore minerals in the dilation openings. Most of the ore is found where the fine-grained dolomite units were so dilated by collapse as to form a series of rubble to crackle breccias. Hypothetical cross sections synthesized from widely spaced drill-hole data show mineralized structures of a size, shape, and distribution of metal comparable to those diagrammed in the literature from actual field relations. From these composite models of hypothetical structures the relative position of a particular hole can be approximated within its own structure. The exploration geologist thus has a numerical aid for estimating the amounts of offset needed to penetrate the most favorable part of the mineralized collapse structure with second-stage drill holes.

Economic Geology↗

USGS1971

Evidence on the age mineralization in the of east of barite, zinc, and iron lower paleozoic rocks Tennessee

Based on a study of minor occurrences of zinc, barite, and iron in East Tennessee, certain deposits are interpreted to have formed during early Middle Ordovician time. Principal lines of evidence supporting this age are: (1) the occurrence of barite, sphalerite, and pyrite associated with synsedimentary collapse breccias which span the pre-Middle Ordovician unconformity at the Lost Creek barite mine in Union County; (2) barite in basal Middle Ordovician beds (Athens Shale and Lenoir Limestone) in northeastern Tennessee and southwestern Virginia; (3) sphalerite and pyrite in dolomite filling paleocaves in the uppermost part of the Lower Ordovician Mascot Dolomite at the Trotter prospect near Douglas Dam in Sevier County; and (4) oolitic hematite and pyritiferous beds near the base of the Athens Shale and subjacent pyritiferous collapse breccias in the Mascot and Kingsport Formations at several localities along the eastern side of the Appalachian Valley. Thus, it is concluded that ascending solutions formed epigenetic deposits in pre-Middle Ordovician carbonate strata nearly contemporaneously with syngenetic deposits in early Middle Ordovician sediments. These findings are in general accord with those of recent workers in the Mascot-Jefferson City and Copper Ridge districts who have proposed that mineralization in these areas occurred during the time interval of pre-Middle Ordovician erosion. The long-held theory which associates mineralization with late Paleozoic diastrophism is not supported.

Tennessee↗

USGS1953

Reconnaissance for radioactive deposits in the Fairbanks and Livengood Quadrangles, east-central Alaska, 1949

Several mines and prospects in the Fairbanks and Livengood quadrangles, east-central Alaska, were examined for the possible presence of radioactive materials in the summer of 1949. Also tested were pre-Cambrian and Paleozoic metamorphic and sedimentary rocks crossed by the Elliott Highway, which extends from Fox, near Fairbanks, northward about 70 miles to the town of Livengood. None of the lodes tested exhibited radioactivity in excess of 0.003 percent equivalent uranium, although nuggets consisting chiefly of native bismuth and containing as much as 0.1 percent equivalent uranium had been found previously in a placer on Fish Creek several miles below the reported bismuth-bearing lode on Melba Creek. The greatest radioactivity found in the rocks along the Elliott Highway was in an iron-stained schist of pre-Cambrian age and in carbonaceous shale of Middle Devonian or Carboniferous age. Respective samples of these rocks contain 0.003 and 0.004 percent equivalent uranium. A possible local bedrock source for a euxenite-polycrase mineral found in a placer concentrate containing about 0.04 percent equivalent uranium was sought in the watershed of Goodluck Creek, near Livengood. The bedrock source of this mineral could not be located; it is believed that the source could be outside of the Goodluck watershed, as drainage changes in the area during Quaternary time might well have introduced gravels from nearby areas.

Alaska↗